Project Summary/Abstract: The main focus of research in our group is to understand the underlying molecular mechanisms of pancreatic and breast cancer pathogenesis. The overarching goal of our research is to investigate how the cellular pathways (i.e. circuits) are dysregulated and can lead to uncontrolled cell growth (i.e. cancer). The ultimate goal is to develop and use small molecules to target the dysregulated proteins that are the underlying cause of pancreatic and breast cancers pathogenesis. Our laboratory has been working with a group of proteins, called Mixed Lineage Kinases (MLKs). The roles of MLKs in cancer is an emerging area and the inhibitor of this family has gone through clinical trial for Parkinson's Disease. We have shown that inhibitor of MLKs can be repurposed to treat Triple Negative breast cancer (TNBC) and pancreatic ductal adenocarcinoma (PDAC). Our recent results (funded through VA-Merit) demonstrate that one of the MLK family member, MLK3 was highly overexpressed in human pancreatic cancer tumors and was necessary for cell growth. Furthermore, using animal models of pancreatic cancer, we have observed that MLKs inhibitor ameliorate PDAC and the animals survive much longer, compared to vehicle treated animals. We plan to further explore how MLK3 dysregulation promotes pancreatic cancer and ultimately use the inhibitors for therapeutic intervention. The other two projects (funded through 2 NCI/NIH grants) are on breast cancer. We reported earlier that suppression of MLK3 activity by Estrogen was necessary for ER+ breast cancer cell survival and growth. We also observed that the other receptor, HER2 was also able to suppress MLK3 activity in HER2+ breast cancer and this was also necessary for their survival. Taken together, these exciting results suggest that suppression of MLK3 by ER and HER2 provides survival signals for breast cancer cell growth and proliferation. Therefore, we developed a novel nanoparticle, loaded with MLK3 activator, ceramide (a lipid) that was able to induce significant cell death in HER2+ and ER+ breast cancer cells. In animal models of ER+ and HER2+ breast cancer, the ceramide-nanoparticle was able to reduce tumor burden. In addition, we also observed that in human TNBC tumors, the activity of MLK3 was very high compared to ER+ breast cancer tumors. Through mechanistic studies, we identified that MLK3 activity plays paradoxically a survival role in TNBC. Based on our cellular and human tumor data, the animal transplanted with TNBC tumors (i.e. PDXs) were treated with MLKs inhibitors, indeed the tumor burden was reduced and the animal life was prolonged. Our results are first in line to demonstrate that MLK3/MLKs inhibitors can significantly reduce TNBC tumor burden and can prolog animals' life. Similarly, following our cellular and human tumor data, the tumor burden of Herceptin (i.e. anti-HER2+ therapy) resistant human tumors in animal (i.e. PDXs) was reduced. Taken together, our results suggest conclusively that activator of MLK3/MLKs could be used to treat ER+ and HER2+ breast cancer, whereas the inhibitor of MLK3/MLKs could serve as a therapeutic intervention for TNBC and pancreatic ductal adenocarcinoma (PDAC). Our comprehensive studies also suggest that it is utmost important to understand the detail underlying molecular mechanisms of a disease before using any targeted therapy.